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F-4377 — Revert NULL-hierarchy reject; NULL tickets are spec-compliant

pull/512/head
aidan garske 2026-05-26 13:40:33 -07:00
parent 48eaf5cfe6
commit a53c28be00
2 changed files with 0 additions and 57 deletions
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7
src/fwtpm/fwtpm_command.c
View File

@ -8861,13 +8861,6 @@ static TPM_RC FwCmd_PolicyAuthorize(FWTPM_CTX* ctx, TPM2_Packet* cmd,
if (rc == 0 && ticketTag != TPM_ST_VERIFIED) {
rc = TPM_RC_TICKET;
}
/* Per TPM 2.0 Part 3 Sec.23.16, a TPMT_TK_VERIFIED with
* hierarchy == TPM_RH_NULL is invalid input. Reject before
* HMAC verification to prevent a NULL-hierarchy proofValue
* being fed into FwComputeTicketHmac. */
if (rc == 0 && ticketHier == TPM_RH_NULL) {
rc = TPM_RC_HIERARCHY;
}
/* Verify ticket HMAC per TPM 2.0 Part 3 Section 23.16:
* 1. Compute aHash = H(approvedPolicy || policyRef)
* 2. Ticket from VerifySignature is HMAC(proofValue, aHash || keyName)

50
tests/fwtpm_unit_tests.c
View File

@ -6857,55 +6857,6 @@ static void test_fwtpm_policy_pcr(void)
fwtpm_pass("PolicyPCR:", 0);
}
/* Per TPM 2.0 Part 3 Sec.23.16, a TPMT_TK_VERIFIED with hierarchy ==
* TPM_RH_NULL is invalid input and must be rejected with
* TPM_RC_HIERARCHY. Without this guard the handler proceeds into HMAC
* verification with a NULL-hierarchy proofValue, which an attacker can
* pair with a zero-digest ticket to fabricate PolicyAuthorize extensions. */
static void test_fwtpm_policy_authorize_null_hierarchy_rejected(void)
{
FWTPM_CTX ctx;
UINT32 sessH;
int pos, rspSize;
byte fakeKeyName[34];
byte fakeDigest[32];
memset(&ctx, 0, sizeof(ctx));
AssertIntEQ(fwtpm_test_startup(&ctx), 0);
sessH = StartSessionHelper(&ctx, TPM_SE_POLICY);
AssertIntNE(sessH, 0);
PutU16BE(fakeKeyName, TPM_ALG_SHA256);
memset(fakeKeyName + 2, 0xCD, 32);
memset(fakeDigest, 0xEF, sizeof(fakeDigest));
pos = 0;
PutU16BE(gCmd + pos, TPM_ST_SESSIONS); pos += 2;
PutU32BE(gCmd + pos, 0); pos += 4;
PutU32BE(gCmd + pos, TPM_CC_PolicyAuthorize); pos += 4;
PutU32BE(gCmd + pos, sessH); pos += 4;
pos = AppendPwAuth(gCmd, pos, NULL, 0);
PutU16BE(gCmd + pos, 32); pos += 2;
memset(gCmd + pos, 0, 32); pos += 32; /* approvedPolicy */
PutU16BE(gCmd + pos, 0); pos += 2; /* policyRef */
PutU16BE(gCmd + pos, sizeof(fakeKeyName)); pos += 2;
memcpy(gCmd + pos, fakeKeyName, sizeof(fakeKeyName));
pos += sizeof(fakeKeyName);
/* TPMT_TK_VERIFIED: tag | hierarchy=NULL | digest(32 garbage bytes) */
PutU16BE(gCmd + pos, TPM_ST_VERIFIED); pos += 2;
PutU32BE(gCmd + pos, TPM_RH_NULL); pos += 4;
PutU16BE(gCmd + pos, sizeof(fakeDigest)); pos += 2;
memcpy(gCmd + pos, fakeDigest, sizeof(fakeDigest));
pos += sizeof(fakeDigest);
PutU32BE(gCmd + 2, (UINT32)pos);
rspSize = 0;
FWTPM_ProcessCommand(&ctx, gCmd, pos, gRsp, &rspSize, 0);
AssertIntEQ(GetRspRC(gRsp), TPM_RC_HIERARCHY);
FlushHandle(&ctx, sessH);
FWTPM_Cleanup(&ctx);
fwtpm_pass("PolicyAuthorize NULL hierarchy (HIERARCHY):", 0);
}
#endif /* !FWTPM_NO_POLICY */
/* ================================================================== */
@ -8281,7 +8232,6 @@ int fwtpm_unit_tests(int argc, char *argv[])
test_fwtpm_policy_command_code();
test_fwtpm_policy_locality();
test_fwtpm_policy_pcr();
test_fwtpm_policy_authorize_null_hierarchy_rejected();
#endif
/* NV operations */